The present invention relates to a coincidence testing method for enhancing the reliability of the output data from a label reader. Recently, computer based systems for inventory control have seen widespread use in supermarkets, department stores, and the like. The successful operation of these computerized inventory systems is dependent, typically, upon the ability of certain peripheral equipment known as label readers to reliably read data encoded into the labels associated with the inventory items and to provide correct data to the computer.
Typical label codes include so-called bar codes consisting of a plurality of bars with different widths or colors. The arrangement of the bars in such a code can be interpreted to identify the particular goods and the like. Such bar codes are usually printed on a price tag or other label associated with the goods.
However, printed bar codes frequently suffer from defects such as blurring, incomplete or defective bar shapes, bar inclination, fading and similar problems. Such defective bar codes may result in erroneous readings by the label reader. Reading errors, of course, can also occur due to malfunctions in the label reader itself. If erroneous data is provided to the computer by the label reading peripheral equipment, the computer system will then compound the error, and the inventory control system will be ineffective.